Tertiary mono olefin extraction with mixed acids

ABSTRACT

A liquid refinery hydrocarbon stream containing tertiary olefins is contacted with a mixture of sulfuric acid, water and at least one aliphatic monocarboxylic acid to extract the tertiary olefins from the hydrocarbon stream in an acid extract which may be further reacted directly, or treated to remove the tertiary olefins or the tertiary alcohols in concentrated form.

United States Patent Murphy 1 Feb. 4, 1975 [54] TERTIARY MONO OLEFIN EXTRACTION 3,231,632 1/1966 Friedli et :11. 260/677 5 WITH MIXED ACIDS FOREIGN PATENTS OR APPLICATIONS Inventor: Donald p y, University 683,322 3/1964 Canada 260/677 A Heights, Ohio 1 1 Assignfiei The Goodrich AkfOn, Primary Examiner-Delbert E. Gantz Ohio Assistant Examinerluanita M. Nelson [22] Filed: Oct. 30, 1973 Attorney, Agent, or Firm-J. Hughes Powell, Jr.

A liquid refinery hydrocarbon stream containing ter- [52] 260/677 S, 260/6815 260/677 A tiary olefins is contacted with a mixture of sulfuric Cl. acid ater and at least one aliphatic monocarboxylic 1 Field of Search 260/677 677 6815 R acid to extract the tertiary olefins from the hydrocarbon stream in an acid extract which may be further 1 References Clted reacted directly, or treated to remove the tertiary 01e- UNITED STATES PATENTS fins or the tertiary alcohols in concentrated form.

1,941,267 12/1933 Morrell 208/224 1,941,267 12/1933 MOl'l'B11 208/255 3 Clams N0 Drawmgs 2,515,006 7/1950 Hudson 260/677 R 2,530,332 11/1950 Hudson 260/677 X TERTIARY MONO OLEFIN EXTRACTION WITH MIXED ACIDS BACKGROUND OF THE INVENTION The use of strong polyhasic mineral acids or organic 5 acids or mixtures thereof for the selective extraction of tertiary olefins front a hydrocarbon stream is well known. For example, US. Pat. Nos. 2,007,159 and 2,007,160 teach the use of polybasic mineral acids such as sulfuric or phosphoric acid, or, in certain instances. the use of monobasic acids such as hydrochloric acid or organic acids such as benzenesulfonic acid or the sulfonic acids of the homologs of benzene. U.S. Pat. No. 2,515,006 teaches the use of a mixture of sulfonic acids modified by the presence of a polybasic mineral acid-acting substance such as sulfuric acid or phosphoric acid. US. Pat. No. 2,530,332 teaches the separation of certain tertiary monohexenes from other ter tiary monohexenes, using polybasic mineral acids or mixtures thereof, organic sulfonic acids or mixtures thereof, or mixtures of polybasic and organic sulfonic acids. US. Pat. No. 1,941,267 teaches the use ofa mixture of sulfuric acid, acetic acid and water for vaporphase removal at temperatures from 250 to 600F. of color and gum formers from hydrocarbon oil of motor fuel boiling range without removing unduly large percentages of monoolefins. A new method is desired which does not use the expensive sulfonic acids and is specific for tertiary olefins, resulting in greater tertiary olefin extraction than obtained with sulfuric acid-water extraction.

SUMMARY OF THE INVENTION The method of the present invention comprises contacting a refinery liquid hydrocarbon streamcontaining tertiary olefins, with a mixture of sulfuric acid, water and at least one aliphatic monocarboxylic acid in liquid phase to extract tertiary olefins from the hydrocarbon stream. The extraction process results in greater tertiary olefin extraction than obtained with dilute sulfuric acid alone.

DESCRIPTION OF THE INVENTION A first step toward economic utilization of refinery hydrocarbons is separation by close fractionation into isomeric groups wherein substantially all of the hydrocarbons in a group have about the same number ofcarbon atoms. A next step is the separation of various hydrocarbons within an isomeric group by methods depending upon a marked difference in reactivity of the various hydrocarbons. For example, acetylenes, diolefins and other hydrocarbons more highly unsaturated than monoolefins may be removed by reaction with copper salts or by other methods known to those skilled in the art. Ofthe major remaining compounds, tertiary monoolefins and normal monoolefins are successively less reactive with sulfuric acid, and saturated hydrocarbons (paraffins and cycloaliphatics) are practically inert. The same scale of decreasing reactivities has been found to exist for the mixed acids of the present invention.

The method of the present invention comprises contacting a liquid refinery hydrocarbon stream containing tertiary olefins with a mixture of sulfuric acid, water and at least one aliphatic monocarboxylic acid in liquid phase to extract the tertiary olefins from the hydrocarbon stream. More specifically, the method of the pres- 2 ent invention comprises contacting a liquid refinery hydrocarbon stream containing at least tertiary monoolefins with a mixture of sulfuric acid, water and at least one aliphatic monocarboxylic acid in liquid phase to extract the tertiary monoolefins from the hydrocarbon stream.

The hydrocarbon stream is preferably a C, to C carbon compound fraction, more preferably a C, to C5 fraction. Tertiary olefins are those mono-or diolefins containing in the molecule a double-bonded carbon atom attached to three other carbon atoms, i.e., the four valences of a tertiary carbon atom are occupied by three other carbon atoms. Examples of tertiary olefins include C Compounds such as isobutene; C compounds such as l-methyl-l-butene. Z-methyl-Z-butcne. isoprene and the like; and C compounds such as Z-methyH-pentene, 2-methyl-2-pentene, 3-methyl-2- pentene, and the like. The hydrocarbon stream generally contains from about 0.2% to about 50% by weight. more often from about 1% to about 35% by weight, of said tertiary olefins.

The extraction mixtures are mixtures of sulfuric acid and at least one aliphatic monocarboxylic acid with water. The monocarboxylic acids have from 2 to 6 carbon atoms. More preferred are acetic or propionic acids or mixtures thereof. Even more preferred is acetic acid. Hydrochloric acid and/or nitric acid cannot serve as strong acid replacements for sulfuric acid, since they form undesirable stable compounds with tertiary olefins. The mixture contains about 44% to about 71% by weight of sulfuric acid and front about 1% to about 50% by weight of the weak acid, with the remainder being water. The water is present in a molar ratio of water to olefin of at least 1.5/1 and constitutes the difference between the total acid percentage and 100% of the mixture. More preferably, the mixture contains from about 2% to about 26% by weight of the weak acid. The weight ratio of acid-water mixture to the hydrocarbon stream is at least 0.7/1, more preferably at least H1. The extraction is performed at a temperature of from about 10C to about 50C, more preferably from about 0C to about 30C, and still more preferably from about 0C to about 10C.

Any convenient liquid contacting technique may be used for tertiary olefin extraction in a batch or continuous operation. Tertiary olefins are absorbed effectively by the mixture to form an acid liquor extract which may then be subjected to a reversion agent such as naphtha at a temperature of from about 20C to about C, more preferably from about 22C to about 50C, to recover the extracted tertiary olefins themselves or the tertiary alcohols in concentrated form as is known in the art. Controlled steam stripping may also be used but is less desirable, since it dilutes the acid. Alternatively, the acid extract may be heated further to polymerize the olefins to their dimers, trimers, higher oligomers or to their polymeric form. The extract may also be used directly in effecting chemical reactions between the tertiary olefins and other compounds. Other methods of treating and using the extract are known to those skilled in the art.

The method of the present invention does not use the expensive sulfonic acids of the prior art. This method results in greater tertiary olefin extraction than does use of a sulfuric acid and water mixture wheresulfuric acid isof like concentration.

The corrosive effect of the treating mixtures may be overcome to some extent by controlling sulfuric acid concentration and by the use of acid-resisting metals or suitable linings of the contacting apparatus. For example. the apparatus may be lined with silicate mixtures and cements using water glass, fire clay and the like. or the apparatus may be lined with various enameling compositions.

The tertiary olefins extracted by the process of the present invention are useful in many organic syntheses and polymerization reactions. For example. isobutene is used in the production of isooctane. butyl rubber and polyisobutene resins. 2-methylbutene-2 or 2- methylbutene-l may be dehydrogenated to isoprene. which may bepolymerized to cis-l,4-polyisoprene (synthetic natural rubber), useful in tires and other rubber goods.

The following examples illustrate the present invention more fully. Tertiary amylene extractions were carried out in 500 cc. glass reactors equipped with 600 RPM stirrers and placed in a constant temperature bath. About 150 cc of acid and about 100 cc of hydrocarbon feedstock (containing 19.7% and 23.4% tertiary amylene in Example 1 and Example 2 respectively) were added to each reactor and stirred for three hours. Analyses of hydrocarbon feedstocks are shown in Table 1. The acid-hydrocarbon phases were separated using a separatory funnel and analyzed for tertiary olefin content by gas chromatography. The date (see Table 2) shows substantially greater tertiary olefin extraction solubility with a mixture of sulfuric acid. acetic acid and water than with a mixture of sulfuric acid and water. The acid liquor extract is then contacted with naphtha at 40C to recover the tertiary olefins in concentrated form.

TABLE I Hydrocarbon Feedstock Approximate Wtf/r Components x.1 Ex.2

C, to C compounds lsopentane n-pentane and 3-methyl-l-butene l-pentene Z-methyl-l -butene Trans-Z-pentene Cis-2- entene Z-met yl-Z-butene lsoprcnc Cyclopentene C and higher TABLE 2 Ex. 1 Ex. 2

t l iliquilihrium Constant (Mols 'lcttlar ()lct'ln in Acidllltuls Tertiary Ulcl'm in Hydrocarbunl I claim:

1. A process for extracting tertiary mono olefins from a liquid refinery C to C hydrocarbon stream wherein said stream is contacted with a mixture containing (A) from about 44% to about 71% by weight sulfuric acid, (B) from about 1% to about 50% by weight of at least one aliphatic monocarboxylic acid containing from 2 to 6 carbon atoms, and (C) water in a molar ratio of water to olefin of at least 1.5/1, said water making up the difference between total acid percentage and of said mixture. the weight ratio of said mixture to said bydrocarbon stream is at least 0.7/1, and mixture is contacted with said hydrocarbon stream at a temperature in the range from about -l0C to about 50C.

2. A process of claim 1 wherein said hydrocarbon stream is selected from the group consisting ofC, to C compound fractions, said mixture contains from about 2% to about 26% by weight of an aliphatic monocarboxylie acid selected from the group consisting of acetic acid and propionic acid, the weight ratio of said mixture to said hydrocarbon stream is at least 1/1, said mixture is contacted with said hydrocarbon stream at a temperature of from about 0C to about 30C, and thereafter separated from said acid.

'3. A process of claim 2 wherein said hydrocarbon stream is a C,-, compound fraction, said aliphatic monocarboxylic acid is acetic acid, said hydrocarbon stream is contacted with said mixture at a temperature of from about 0C to about 10C and thereafter separated from said mixture, and said tertiary monoolefins are thereafter recovered from said acid mixture. 

1. A PROCESS FOR EXTRACTING TERTIARY MONO OLEFINS FROM A LIQUID REFINERY C4 TO 6 HYDROCARBON STREAM WHEREIN SAID STREAM IS CONTACTED WITH A MIXTURE CONTAINING (A) FROM ABOUT 44% TO ABOUT 71% BY WEIGHT OF SULFURIC ACID, (B) FROM ABOUT 1% TO ABOUT 50% BY WEIGHT OF AT LEAST ONE ALIPHATIC MONOCARBOXYLIC ACID CONTAINING FROM 2 TO 6 CARBON ATOMS, AND (C) WATER IN A MOLAR RATIO OF WATER OT OLEFIN OF AT LEAST 1.5/1, SAID WATER MAKING UP THE DIFFERENCE BETWEEN TOTAL ACID PERCENTAGE AND 100% OF SAID MIXTURE, THE WEIGHT RATIO OF SAID MIXTURE TO SAID HYDROCARBON STREAM IS AT LEAST 0.7/1, AND MIXTURE IS CONTACTED WITH SAID HYDROCARBON STREAM AT A TEMPERATURE O IN THE RANGE OF FROM ABOUT -10*C TO ABOUT 50*C.
 2. A process of claim 1 wherein said hydrocarbon stream is selected from the group consisting of C4 to C5 compound fractions, said mixture contains from about 2% to about 26% by weight of an aliphatic mOnocarboxylic acid selected from the group consisting of acetic acid and propionic acid, the weight ratio of said mixture to said hydrocarbon stream is at least 1/1, said mixture is contacted with said hydrocarbon stream at a temperature of from about 0*C to about 30*C, and thereafter separated from said acid.
 3. A process of claim 2 wherein said hydrocarbon stream is a C5 compound fraction, said aliphatic monocarboxylic acid is acetic acid, said hydrocarbon stream is contacted with said mixture at a temperature of from about 0*C to about 10*C and thereafter separated from said mixture, and said tertiary monoolefins are thereafter recovered from said acid mixture. 